Transmission acting weird

Hello guys I have a 2005 GMC Sierra duramax 6.6 LLY I recently went to do a trans relearn on the truck (now before I get into detail on the issue I want to clarify that the truck did not do this before I hit trans relearn) so I hit trans relearn on the tuner On the truck, and now every time on the 3-4 shift the truck kicks into neutral but if I let off the throttle it will shift, if I don’t it will kick into limp mode and stay in third gear, and earlier today I pulled over to shut truck off and clear the code, the truck wouldn’t go into park it would only go to neutral wouldn’t even go to reverse so I left it in neutral and cleared the code which is the tcm illumination code and then continued to drive home please help me guys